Conventionally, it is known that a HUD device, which uses a source light to display an image as a virtual image visible to a passenger, may include a projection member on which the virtual image is projected. A projection member disclosed in JP H10-96874 A includes a first transparent plate having a first surface on a front side facing a passenger and a second transparent plate having a second surface on a rear side opposite to the front side. Here, the first transparent plate and the second transparent plate maintain polarization state. This projection member also includes a waveplate interposed between the first and second transparent plates. The waveplate includes a fast axis and a slow axis that retards phase with respect to the fast axis. Then, an s-polarized source light enters the first surface obliquely along the plane of incidence. Here, the waveplate is a ½ wavelength plate that rotates polarization direction by 90°.